Wraithen

Hello all,

Since I got my 8th gen 08 EX Coupe I've noted that the clutch engagement happens very high on the pedal, such that the bottom of the pedal does almost nothing. In fact, I can successfully shift, without fully pressing the clutch to the floor.
Upon performing a shift, clutch disengagement happens almost entirely during the beginning 25% of clutch pedal travel (towards the floor). Likewise, once the shift lever is moved into the next gear, clutch engagement happens almost entirely at the last 25% of travel when releasing the clutch pedal.

In essence, about 50% of my clutch pedal's travel distance is just slack and does nothing. But, the slack is below the engage/disengage point, so I'm not entirely sure if that can be adjusted.

Is this normal behavior or can this be adjusted somehow?

ezone

(Assuming nobody has touched the pedal pushrod adjustment and screwed it up)

It's due for a clutch job NOW.
Do it before it's completely gone and has to be towed.


And.....driver habits are the cause of clutch wear. Could have been the previous owner, or it could be you.

A bad operator can ruin a clutch in seconds. A good driver could have a clutch last the life of the car.

Wraithen

Could you expound on this? I'm not really familiar with the pedal pushrod adjustment.


I don't think it's clutch wear:
The car is only at ~60k miles.
The clutch isn't slipping at all.
The gears don't grind on shifts.
I've been locked out of reverse about probably 3 times, but I think that's normal behavior.
I've driven the car for ~14k miles over about a year and a half and neither the behavior of the clutch nor transmission has changed.

What are your indicators of clutch wear?

ezone

Good. It should never need to be touched unless the clutch master cylinder is replaced.

It's on the pushrod between the pedal and the master. It's where the pedal free play is dialed in during initial setup. Once set correctly it should never change nor need further adjustments.


The free play is the (roughly) 10mm of pedal free movement before it makes contact with the master cylinder and begins to actually do something.

That means nothing.
The life expectancy of a clutch is 100% dependent on the driver.


I've seen people ruin a clutch in a matter of FEET. This guy is one of those idiots:

He's not driving that one home.


========================

Figuring out how to get a car to drive down the road doesn't necessarily mean it's being done the right way.


Transmissions ruined because someone doesn't know how to use the clutch, yes that happens too.


Some people just buy a stick shift car without knowing how to drive it.
I saw a car salesman sell a stick shift car to a someone knowing full well the person couldn't drive a stick..... Their first clutch was ruined at 500 miles. The second clutch ruined at 1200 miles? Trans was damaged by 3000 miles.

I've had to do a 100 mile clutch job more than once..

One driver I know needs a clutch replacement about once a year.

Nobody ever taught these people correct techniques.







The person who bought the brand new car... the shops service manager (at the time) ended up teaching her.


Your entire first post is questioning the behavior of the clutch.

Just what you described:

"Engagement height" rises significantly--- just before the clutch disc is completely worn out.

Shortly after engagement height change becomes apparent, slippage is soon to follow.


HTH

Wraithen

The original post wasn't intended to start a discussion about driving habits. Those have been incessantly discussed everywhere else.

Where did you get this metric from? Are there other related tolerances listed in that same place? Hopefully a manual of some sort?

To clarify:
After 14k miles driven, there has been no change in behavior.
I wasn't provided with the maintenance records when I bought the car.

So one of three conclusions are possible:
-This is normal for the clutch in an 8th Gen Civic.
-The clutch was improperly adjusted either upon replacement or otherwise in the hands of the previous owner.
-Wear has occured on the original clutch, resulting in it's current behavior.

I'm partial to the clutch wear hypothesis, but the absence of slippage is sort of confounding. I have tested:
I've tried starting out in 2nd and 3rd - no slippage.
There was an instance where my tires were iced to the ground. The engine would stall if I let the clutch out at about 3.5k rpm. Unfortunately, the way I had to free the car was to ride the clutch for a second.
There's no sign of slippage in either normal or spirited driving.

I've searched in a bunch of places and I've have yet to find a cohesive consensus on proper engagement height, what could possibly cause it to change, and its relationship to worn components.

In your words, how could a worn clutch disc cause a rise in engagement height?

ezone

Part of that is common mechanical sense, there must be some amount of free play at that location.
SOME is the operative word.
There really is a specification in the FSM, but it's not exactly a simple procedure.

Two millimeters of clearance for the adjustment point above the fulcrum (pedal pivot) might equate to roughly 10mm of free play at the long end of the lever (pedal). That's not exact but that's the idea.

You can confirm, feel, and probably even measure the amount of free play by pushing the clutch pedal gently with one pinky finger.


Free play is necessary to allow for expansion and contraction with widely varying temperatures.
If there were zero free play, the master could be continually applied and cause wear of the throwout bearing, partial disengagement of the clutch, slippage and wear, etc. Similar in effect to continually resting a heavy foot on the clutch pedal while driving.

Same thing goes for the brake master cylinder: If there is insufficient free play between the pedal and booster linkage and the brake master cylinder, the brakes can eventually apply by themselves.


You described the engagement height is rising. That's change.

Not really necessary for this IMO.
No. You have noticed a dramatic change, that is not normal operation....(though it is normal for the situation).
Not likely, and if anyone had made incorrect adjustments I believe you should have noticed problems long before now. Like noticed 13,987 miles ago.

What stands out in my memory is the very few times I've had to deal with a misadjusted clutch has been on hacked up crapwagons where someone didn't seem to have any idea what they were doing (mechanic or DIYer, either one)....and the entire car usually exhibits equal care.
Yes.

Slippage usually won't occur until the very end of the disc life, especially with a low power engine.
You have noticed the typical warning signs, so it's coming soon.
(if this were a V6 Accord I bet it would be slipping already)

If I'm right, it will in the very near future.
Off the top of my head:

The pressure plate might move less than two millimeters between its applied and released positions.

A new clutch disc measures around 8mm thick.
Disc wear limit (replacement spec) is 6mm.

The pressure plate can't continue to squeeze a disc that has worn thinner than about roughly 5mm.

There is a very limited amount of total movement that is built-in to the plate assembly that allows compensation for disc wear throughout its working life.
What you feel in the pedal is the pressure plate nearing its design limit of travel and nearing the limit of it's ability to clamp the clutch disc.

It's running out of room.

The clutch hydraulic system is touted as self adjusting, and it is, but once this wear and travel limit has been reached it cannot compensate further and you begin to feel these changes taking place, and this final stage does occur rather rapidly one it reaches this point. (change in engagement height).

As long as the pressure plate has enough room (travel) to compress (grab) the clutch disc, it won't slip.

Once the disc has worn enough that the pressure plate no longer has sufficient travel to squeeze the disc (apply sufficient clamping force), it will slip.

As this disc wear continues, the feel you get through the pedal will be a continued rise in engagement height until there is no more engagement. At that time the pressure plate will have run out of movement to compensate for disc wear, exhausted its ability to clamp the disc with enough force to prevent it from slipping.


How was that?

Wraithen

Very detailed and logical. Much appreciated sir.

I see what you're saying, but that is under the assumption that the self-adjusting hydraulic system is in good condition. I think the clutch master cylinder may be the defective part in this rather than the clutch disc.

Wouldn't the symptoms be similar at this point being that there's no evidence of slippage?

ezone

"Self adjust" is by hydraulic system design and occurs each time you take your foot off of the clutch pedal.

If you've ever had a car that used a cable operated clutch, most of those needed periodic manual adjustment as the clutch disc wears, and as the cable stretches. On those too, as the disc is nearing the end of its life the engagement feeling changes and you can't 'adjust' that out of it.....much as you described the change in engagement height in your car.
I still think yours is probably near the end of its useful life.

The only way I can see this (picture this in my head) as failing anywhere close to the way you describe yours, is if the compensating port (internal) were blocked so the fluid in the hydraulic system couldn't return to the reservoir when your foot is removed from the clutch pedal.

You can prove this compensating port issus is OK by using your hand to retract (push) the (fork and) slave pushrod all the way into the slave cylinder on the transmission. Fluid will flow into the reservoir as you compress the slave. (you will have to pump the pedal up again, and it may lay on the floor the first couple tries)

Simple bleeding of the system can also confirm correct fluid flow and hydraulic operation.


The only times I've seen this particular problem (blocked compensating port) is after someone dumped oil (petroleum) into a hydraulic brake or clutch system, and when something has been misadjusted for some reason causing the master to be partially applied.


WHEN this has been the case, temperature is THE influence on how it acts. Clutch slippage was very evident as everything got warmer with use, less evident when everything is cold. (Engine heat warms up everything in the engine compartment, fluid expands inside the system, the resulting expansion causes the slave cylinder to extend, that's the only place the trapped and expanding fluid can go when it can't go into the fluid reservoir.)

Most hydraulic and master cylinder problems (IMO) result in a LOW pedal engagement height, to the eventual point that it becomes difficult to engage/shift gears or grinds because the pressure plate can't fully release the disc.


If I've driven one, I've driven thousands.
If I've diagnosed and replaced one clutch, I've done it hundreds of times....

I've noted or warned that a clutch will be needed in the near future far more often than I actually get to do the job. (they always have someone who will do it cheaper LOL)

If you've never personally dealt with any clutch difficulties before, it can be a learning experience.....one that may be really difficult to find in print. There are several different possible components that can fail in several different ways, and may have seemingly similar but slightly different symptoms....

Most only generate limited specific user complaints: Something feels wrong, sounds wrong, or the car quit moving.


HTH